It seems that there is no visual hint in Camtasia Producer 9 of which project canvas dimension is in use; you have to choose 'File \ Project Settings' to find this information. It's no handy ...
I brought this idea up to our product team and we all think that this is an interesting idea that we will keep in mind while reviewing some potential UI tweaks.
Feel free to reach out to me if you have any more input on the idea of adding canvas dimensions to the project screen.